FUEL SYSTEM (DFI) 3-79

Oxygen Sensor - not activated (Service Code 33 (Equipped Models))

Oxygen Sensor Removal/Installation

•Refer to the Oxygen Sensor Removal/Installation (Equipped Models) in the Electrical System chapter.

Oxygen Sensor Inspection

•Warm up the engine thoroughly until the radiator fan starts.

•Turn the ignition switch OFF.

•Remove:

Air Cleaner Housing (see Air Cleaner Housing Removal) Primary Fuel Hose (see Fuel Hose Replacement in the Periodic Maintenance chapter)

Oxygen Sensor Lead Connector [A]

•Connect the harness adapter [A] between the main harness connector and oxygen sensor lead connector as shown in the figure.

Main Harness [B]

Oxygen Sensor [C]

Special Tool - Measuring Adapter: 57001-1700

•Connect a digital meter [D] to the harness adapter leads.

Oxygen Sensor Output Voltage

Connections to Adapter:

Digital Meter (+) → R (sensor BK) lead

Digital Meter (–) → BK (sensor GY) lead

•Separate the air switching valve hoses [A] from the air suction valve covers.

○Do not disconnect the air switching valve connector [B].

3-80 FUEL SYSTEM (DFI)

Oxygen Sensor - not activated (Service Code 33 (Equipped Models))

•Install the suitable plugs [A] on the fitting of the air suction valve covers, and shut off the secondary air.

•Connect the following parts temporarily. Fuel Pump Lead Connector [A] Extension Tube [B]

Air Cleaner Housing (see Air Cleaner Housing Installation)

Special Tool - Extension Tube: 57001-1578

•Start the engine, and let it idle.

•Measure the output voltage with the connector joined.

Output Voltage (with Plugs)

Standard: DC 0.8 V or more

•Next, remove the plugs from the fittings [A] with idling.

•Measure the output voltage with the connector joined.

Output Voltage (without Plugs) Standard: DC 0.24 V or less

•Turn the ignition switch OFF.

If the reading is out of the standard (with plugs: DC 0.8 V or more, without plugs: DC 0.24 V or less), remove the ECU and check the wiring for continuity between main harness connectors.

Special Tool - Hand Tester: 57001-1394

○Disconnect the ECU and sensor connectors.

Wiring Continuity Inspection

ECU Connector [A] ←→

Oxygen Sensor Connector [B]

W/BL lead (ECU terminal 30) [C]

BR/BK lead (ECU terminal 28) [D]

If the wiring is good, replace the sensor.

If the reading is within the standard (with plugs: DC 0.8 V or more, without plugs: DC 0.24 V or less), check the ECU for its ground and power supply (see ECU Power Supply Inspection).

If the ground and power supply are good, replace the ECU (see ECU Removal/Installation).

FUEL SYSTEM (DFI) 3-81

Oxygen Sensor - not activated (Service Code 33 (Equipped Models))

Oxygen Sensor Circuit

1.Ignition Switch

2.Oxygen Sensor

3.ECU

4.Fuse Box

5.Oxygen Sensor Heater Fuse 10 A

6.Battery 12 V 8 Ah

7.Main Fuse 30 A